Lasers typically emit coherent beams of monochromatic light, and are ubiquitous in many fields of technology. Many types of lasers exist, each with characteristics that may be optimized for a specific application space. For example, semiconductor diode lasers typically operate at very low power (<1 W) but may be modulated at very high frequencies (>1 GHz). In contrast, many solid-state or fiber-based lasers operate at higher power (e.g., at tens or even hundreds of watts), but are difficult to modulate, as it is challenging to quickly turn the high-power beam on and off without damaging the laser. And, while specialized solutions exist for modulating high-power fiber lasers at constant frequencies, modulating high-power lasers at random frequencies is exceedingly difficult. Random modulation is necessary for applications involving real-time analysis or interpretation of a random data stream, e.g., a digital representation of text, graphics, or other irregular data.
An important metric of laser performance is the “beam quality” of the laser (represented as M2), which is a measure of the laser light collimation. A beam quality equal to one represents a diffraction-limited Gaussian beam. Semiconductor diode lasers typically have high (i.e., non-ideal) beam quality values (e.g., greater than 5, and up to several hundreds or even thousands). Solid-state and fiber lasers may have beam quality values much closer to unity (e.g., 1.1-2), making them more suitable for applications such as drilling, cutting, and printing. High beam quality (i.e., beam qualities close to unity) enables the preservation of the energy and spot size of the beam even after traveling long distances.
There exists a set of potential applications in need of a laser apparatus combining high power, high beam quality, and random modulation. Exemplary applications include three-dimensional printing, precision cutting, bio-medical and dental applications, military and LIDAR applications, among others. Another such application is plateless lithographic printing (such as that described in U.S. Patent Application Publication No. 2010/0031838 (the '838 application), the entire disclosure of which is incorporated by reference herein), in which a laser, modulated at a random frequency that depends upon an unknown data stream, is utilized to modify the ink and/or fountain solution on a printing cylinder without the use of traditional printing plates. The ink is then transferred to a permanent recording medium, and each transfer of ink may be different from the previous one. While plateless lithographic printing may be performed utilizing prior-art lasers, such systems are typically more complex and/or expensive than those described herein, and may operate at slower rates—a considerable disadvantage in commercial printing environments.